Rigid polyurethane foams from polyesters, polyether polyols and hydroxyl-containing copolymers



United States Patent RIGID POLYURETHANE FOAMS FROM POLY- ESTERS,POLYETHER POLYOLS AND HY- DROXYL-CONTAINING COPOLYMERS Charles R.Bearden, David H. Swisher, and David C. Garms, Lake Jackson, Tex.,assignors to The Dow Chemical Company, Midland, Mich., a corporation ofDelaware N0 Drawing. Filed Mar. 25, 1965, Ser. No. 442,783 Claims. (Cl.260-25) ABSTRACT OF THE DISCLOSURE The invention concerns polyurethanesthat are the reaction product of an organic polyisocyanate and (1) acopolymer of a hydroxyl alkyl acrylate and a vinyl aromatic compound,(2) an unsaturated polyester that is the reaction product of thehalf-ester of maleic anhydride and a hydroxyalkyl acrylate reacted witha diglycidyl ether of a bisphenol and interpolymerized with a vinylaromatic compound, and (3) a polyether polyol that is the condensationproduct of an alkylene oxide having from 2 t0 3 carbon atoms in themolecule with a polyhydric alcohol having from 2 to 8 hydroxyl groups,which polyol has from 8 to 30 percent ethylene oxide moieties and an OHequivalent weight of from 60 to 120.

This invention concerns new polyurethane foam products and relates to amethod of making the same. It pertains especially to rigid polyurethanefoams having high load bearing properties.

It is known to prepare polyurethane foams by reacting a polyetherpolyol, such as a condensate of propylene oxide and a polyhydric alcoholhaving three or more hydroxyl groups, or a hydroxyl-containingpolyester, with a polyisocyanate in excess of that theoreticallyrequired to react with the active hydrogens in the mixture ofingredients, and in admixture with a volatile organic blowing agent.Such foams are useful for a variety of purposes in the home andindustry. However, the polyurethane foams often have lower load bearingproperties than is desired for many purposes, which restricts greatlythe uses for which they are otherwise well suited.

Accordingly, it is a primary object of the invention to provide newpolyurethane foams having high load bearing properties. Another objectis to provide a method for making rigid polyurethane foams having highload bearing characteristics, and low density. Other and related objectsmay appear from the following description of the invention.

' According to the invention, rigid polyurethane foams having high loadbearing characteristics, together with good tensile strength, solventresistance and other advantages can readily be prepared by reacting (1)from 20 to 35 percent by weight of a copolymer of from 30-50 percent byweight of a hydroxyalkyl acrylate having the general formula wherein Ris a member of the group consisting of hydrogen and the methyl radicaland n is a whole number from 2 to 3, and correspondingly from 70-50percent by weight of a monovinyl aromatic compound having the generalformula QMSCH.

3,404,107 Patented Oct. 1, 1968 "ice wherein X and Y each represents amember of the group consisting of hydrogen, alkyl radicals having from 1t0 3 carbon atoms and halogen, which copolymer has a molecular weightbetween about 800 and 1400, (2) from 20. to 50 percent by weight of anunsaturated polyester that is the reaction product of (a) the half-esterof maleic anhydride and a hydroxyalkyl acrylate having the above generalformula, and (b) an epoxy resin that is the glycidyl ether of abisphenol having the general formula wherein R and R each representshydrogen, chlorine or bromine, and which epoxy resin or glycidyl etherhas an epoxy equivalent weight of from about 170 to 250,interpolymerized with (c) a monovinyl aromatic compound having the abovegeneral formula to form a final rigid thermoset product from 20 to 50percent by weight of a polyether polyol that is the condensation productof a polyhydric compound having from 2 to 8 OH groups in the moleculeand an alkylene oxide having from 2 t0 3 carbons with the proviso thatnot more than 20 percent of the alkylene oxide moieties are ethyleneoxide moieties and which polyether polyol has an OH equivalent weight offrom 60 to 120, with (3) an approximately chemically equivalent amount,of a polyisocyanate, e.g., from about 0.95 to 1.05, NCO groups for eachOH group in the copolymer, the unsaturated polyester, and the polyetherpolyol, While the ingredients are mixed with, or are i admixture with, aminor amount of a volatile organic liquid blowing agent that is misciblewith or is a solvent for the copolymer and the polyester startingmaterials.

The copolymer Starting material can be prepared by polymerizing amixture of a hydroxyalkyl acrylate having the aforementioned generalformula such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,hydroxypropyl acrylate, hydroxypropyl methacrylate, or a mixture of anytwo or more of such hydroxya-lkyl acrylates and a vinyl aromaticcompound having the aforementioned general formula, e.g. styrene,vinyltoluene, vinylxylene, ethylvinylbenzene, isopropylstyrene,tert.-butylstyrene, chloro'styrene, or dichlorosty-rene, in the desiredproportions, at temperature between and C., in admixture with a solventor an organic liquid which may act as a polymerization chain lengthregulator, or in the presence of carbon tetrachloride or lauroylmercaptan, to form a copolymer having a molecular weight of from 800 to1400, and which is soluble in, or mixable with the unsaturated polyesterstarting material employed. The copolymer can be used in amounts of fromabout 25 to 60 percent by weight of the sum of the weights of thecopolymer and the unsaturated polyester initially used, and saidpolyester is correspondingly employed in amounts of from 75 to 40percent by weight of the 'sum of said ingredients.

The unsaturated polyester starting material is the reaction product of(a) the half-ester of maleic anhydride and a hydroxyalkyl acrylate suchas 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropylacrylate or hydroxypropyl methacrylate, and (b) a stoichiometric amountof an epoxy resin that is the glycidyl ether of a bisphenol or ahalogenated bisphenol having the aforementioned general formula andhaving an epoxy equivalent weight between about and 250,interpolymerized with (c) a monovinyl aromatic compound, e.g. styrene,having the aforementioned formula, to form a final product having amolecular weight corresponding to an absolute viscosity of from 5 to2000 centipoise at 25 C.

The polyether polyol can be the reaction product of a mixture ofethylene oxide and propylene oxide, or of propylene oxide alone or ofpropylene oxide followed by ethylene oxide with polyhydric alcohols suchas water, ethylene glycol, propylene glycol, glycerine, pentaerythritol,trimethylol propane, pentaglycerol, sorbitol, mannitol, sucrose,1,2,4-trihydroxybenzene, 1,3,5-trihydroxybenzene or1,2,3,S-tetrahydroxybenzene, which reaction product has an OH equivalentweight between 60 and 120.

The polyisocyanate can be tolylene diisocyanate (TDI),diphenylmethane-4,4'-diisocyanate (MDI), polymethylene'polyphenylisocyanate (PAPI), dianisidine, diisocyanate (DADI),triphenylmethane triisocyanate, or hexamethylene diisocyanate. Thepolyisocyanate is employed in amount corresponding to about astoichiometric amount of one NCO group, preferably from about 1 to 1.05NCO groups for each active OH and/ or H group in the mixture ofingredients.

In practice the polyurethane foams are prepared by reacting a mixture ofthe copolymer, the polyester and the polyether polyol in proportions ashereinbefore stated and in admixture with a volatile organic liquidblowing agent that is miscible with, or a solvent for said ingredients,with the polyisocyanate, and advantageously in admixture with a cellregulating agent and one or more catalysts for the urethane reaction.

Among volatile organic substances that are suitable as solvents for thecopolymer and as blowing agents for the foam there may be mentioned asexamples, ethyl chloride, methyl chloride, isopropyl chloride,vinylidene chloride, acetone, methyl ethyl ketone, methylene chloride,carbon tetrachloride, chloroform and mixtures of such compounds withfluorine-containing compounds such as trichlorofluoromethane,dichlorodifluoromethane, trifluoromethane, chlorotrifluoromethane, ordichlorotetrafluoroethane.

Suitable cell-control agents are the silicone-glycol surfactants such asthe polyoxyalkylene block copolymers having the general formula whereinC H O is a mixed polyoxyethylene-polyoxypropylene "block copolymercontaining about 17 oxyethylene units and about 13 oxypropylene units,and of the type disclosed in United States Patent No. 2,834,748, andsilicone-glycol copolymers of the Dow Corning 202 surfactant type ordimethyl polysiloxane fluids.

Among suitable catalysts for the polyurethane reaction are the aminessuch as triethylenediamine, N-ethylmor-pholine, N-methylrnorpholine,N,N,N',N'-tetramethylbutane diamine, and metal salts such as 'stannousoctoate, stannous oleate, dibutyltin dioctoate, and dibutyltindilaurate.

Polymerization initiators or catalysts are methyl ethyl ketone peroxide,a,ot-azobisisobutyronitrile, octyl peroxide a,u-azobisisobutyronitrile,acetyl peroxide, benzoyl peroxide, tert.- butyl peracetate,tert.-butyl-perbenzoate, or dicumyl peroxide. The catalyst is employedin amounts of from 0.2 to 2.5 percent by weight of the polyesterstarting material.

Driers such as cobalt naphthenate, manganese naphthenate, cobaltlinoleate, or manganese linoleate, can advantageously be added to thepolyester in amounts of from about 0.25 to 1.75 percent by weight, toaccelerate the polymerization reaction.

The following examples illustrate ways in which the principle of theinvention has been applied, but are not to be construed as limiting itsscope.

EXAMPLE 1 (A) A charge of 98 parts by weight of maleic anhytlride wasmixed with U6 parts by weight of Z-hydroxyethyl acrylate in a reactionvessel equipped with a reflux condenser and stirrer. The mixture wasstirred at temperatures between about C. and C. for a period of 90minutes. The reaction product was the half-ester of maleic anhydridehaving the formula The half-ester is a liquid which gels below itsboiling point and has a refractive index of 11 1.4839.

(B) A charge of 214 parts by weight of the half-ester of maleicanhydride and Z-hydroxyethyl acrylate, prepared in part A above, wasmixed with parts by weight of diglycidyl ether of bisphenol A having theformula Epoxy Resin D.E.R. 332, having an epoxy equivalent weight of 172and a viscosity of 4000 centipoises at 25 C.

To the reacted mixture there was added 576 parts by weight of styrene.The resulting mixture was stirred and maintained at tempertaures between50 and 70 C. for a period of 1-2 hours. The product was an unsaturatedpolyester having an average molecular weight of 1000, an absoluteviscosity of 5 centipoise at 25 C., and 0.9 percent acidity calculatedas COOH.

(C) A copolymer was prepared by mixing 40 parts by weight of2-hydroxyethyl acrylate and 60 parts by weight of styrene with 100 partsby Weight of carbon tetrachloride as solvent and reaction medium in aglass reaction vessel equipped with a reflux condenser and stirrer. Onepart by weight of benzoyl peroxide was added as catalyst. The resultingmixture was stirred and was heated at refluxing temperatures for aperiod of 10 hours to polymerize the monomers. Thereafter, a portion ofthe carbon tetrachloride was distilled from the mixture. The residue wasplaced in a shallow dish in a vacuum oven and was maintained at atemperature of about 40 C. for 16 hours under 3 millimeters absolutepressure. The copolymer was a friable, brittle solid that was easilycrushed to a powder. The copolymer contained 40 percent by WeightZ-hydroxyethyl acrylate, by analysis, The copolymer had a viscositycharacteristic of 5 centistokes at 100 F. as determined for a 50 weightsolution of the copolymer in methyl ethyl ketone.

(D) A polyurethane foam was prepared from a mixture of the copolymerprepared in part A above, the unsaturated polyester prepared in part Cabove and a polyol consisting of the condensation product of propyleneoxide with a mixture of 2.5 moles of glycerine, 1 mole of sucrose and0.5 mole of water in amount of 1 mole of the propylene oxide for each OHgroup in the mixture of the ingredients to form a polyol product havingan average molecular weight of 540, employing procedure and ingredientsas follows:

A charge of 50 parts by weight of the copolymer prepared in part A abovewas mixed with 100 parts by weight of the unsaturated polyester preparedin part C above and 50 parts of the polyether polyol. The resultingmixture was stirred at room temperature until the copolymer wasdissolved. Stirring was continued while adding 0.75 part by weight oftriethylenediamine and 1.5 parts by weight of silicone oil DG-20, ascatalyst and cell regulating agent, respectively, to the mixture.Thereafter, there was added in sequence with stirring 40 parts by weightof trichlorofluoromethane and 45 parts by weight of tolylenediisocyanate. After adding the tolylene diisocyanate as the finalingredient the mixture was stirred for 60 seconds, then was poured intoa cylindrical mold 6 inches in diameter, by 5 inches high and wasallowed to react. The mixture foamed to a cellular mass 7 inches high ina period of 150 seconds, then set to a rigid body. The foam was composedof uniform fine closed cells and had a density of 5 lb./ft.

EXAMPLE 2 (A) A copolymer of 40 percent by weight of 2-hydroxyethylacrylate and 60 percent by weight of styrene, having a viscositycharacteristic of 5 centistokes at 100 F. as determined for a 50 weightpercent solution of the copolymer in methyl ethyl ketone, was preparedemploying procedure similar to that employed in part A of Example 1.

(B) A polyurethane foam was prepared from a mixture of the copolymerdescribed in part A of this example, a portion of the unsaturatedpolyester prepared in part C of Example 1, a polyether polyol asemployed in Example 1, employing procedure similar to that employed inpart D of Example 1 and ingredients as follows.

Methyl ethyl ketone peroxide 3.0 Tolylene diisocyanate 45Trichlorofluoromethane 45 The mixture of ingredients were blendedtogether by vigorous stirring for a period of 60 seconds, then waspoured into a paper cup and allowed to foam. The product was a cellularmass of uniform small cells and had a density of 6 lb./ft.

EXAMPLE 3 (A) A copolymer of 60 percent by weight styrene and 40 percentby weight hydroxypropyl acrylate, having a viscosity characteristic of 6centistokes at 100 F. as determined for a 50 weight percent solution ofthe copolymer in methyl ethyl ketone, was prepared by procedure similarto that employed in part A of Example 1.

(B) A polyurethane foam was prepared from a mixture of the copolymerprepared in part A of this example, a portion of the unsaturatedpolyester prepared in part C of Example 1, and a polyether polyol asemployed in Example 1, employing procedure similar to that employed inpart D of Example 1 and ingredients as follows:

Ingredient: Parts by weight Copolymer 50 Polyether polyol 50 Siliconeoil (L-520) 3 Stannous octoate 2.5 Tolylene diisocyanate 45 Methylenechloride 45 Polyester (Ex. 1) 50 u, x-azobisisobutyronitrile 0.2

The foam product was cellular mass having a density of 2.5 lbs./cu. ft.

We claim:

1. An organic cellular polyurethane product comprising (1) from 20 to 35weight percent of a copolymer of (a) from 30 to 50 percent by weight ofa hydroxyalkyl acrylate monomer having the general formula R o HzC=( 7iOCnHznOH wherein R is a member of the group consisting of hydrogen andthe methyl radical and n is a whole number between 2 and 3, and (b)correspondingly from 70 to 50 percent by weight of a vinylidene aromaticmonomer having the general formula CH R wherein R and R each representsa member of the group consisting of hydrogen, chlorine and bromine, andwhich epoxy resin has an epoxy equivalent weight of from 170 to 250,interpolymerized with (c) a vinyl aromatic monomer having the aboveformula to form a final polyester product having anabsolute viscosity offrom 5 to 2000 centipoises at 25 C., and (3) from 20 to 50 weightpercent of a polyether polyol that is the condensation product of analkylene oxide having from 2 to 3 carbons and a polyhydric alcoholhaving from 2 to 8 hydroxyl groups with the proviso that from 8 to 30percent of the alkylene oxide moieties are ethylene oxide moieties andsaid polyether polyol has an OH equivalent weight of from 60 to 1.20,reacted with an approximately stoichiometric amount of a polyisocyanatecorresponding to from about one NCO group for each OH group in saidmixture of ingredients, while dissolved in and in admixture with avolatile organic substance boiling below 110 C. as blowing agent toproduce said cellular polyurethane product.

2. A cellular polyurethane product as claimed in claim 1 wherein thecopolymer is a copolymer of 2-hydroxyalkyl acrylate and styrene.

3. A cellular polyurethane product as claimed in claim 1 wherein thepolyester is the reaction product of the halfester of maleic anhydrideand 2-hydroxyethyl acrylate reacted with diglycidyl ether of4,4-isopropylidene diphenol and interpolymerized with styrene.

4. A cellular polyurethane product as claimed in claim. 1 wherein thepolyether polyol is the condensate of propylene oxide with a mixture ofabout 2.5 moles of glycerine 1.0 mole of sucrose and 0.5 mole of water,in amount corresponding to about 4 moles of the propylene oxide.

5. A cellular polyurethane product as claimed in claim 1 wherein thecopolymer is a copolymer of hydroxypropyl acrylate and styrene.

References Cited UNITED STATES PATENTS 3,294,711 12/1966 Von Bonin260-25 3,304,273 2/ 1967 Stamburger 260- 3,314,901 4/1967 Daumiller etal 260-25 DONALD E. CZAJA, Primary Examiner,

W. E. PARKER, Assistant Examiner,

